With reference to FIGS. 1-3, filters for treatment of flue gas comprise a structure 1 with a C-shaped profile 2 and a plurality of filter bags 3 (also hundreds or thousand) through which the flue gas is conveyed to remove dust and particles from them. Arrows FG shows the flue gas directed through the filter bags 3 and arrows CFG shows the flue gas directed to further treatment after dust and particle removal.
The filter bags 3 need periodical cleaning to maintain their efficiency.
In order to clean the filter bags 3, nozzle pipes 4 are provided that carry nozzles 5; each nozzle 5 is aligned with a filter bag 3. Each nozzle pipe 4 is connected at one side to a pipe 6 in turn connected to a pressure vessel 7a with a valve 7b, supplied by a compressor 7c that supply compressed air to clean the filter bags 3, and at the other side it is connected to and supported by the C-shaped profile 2.
The connection of the nozzle pipe 4 to the C-shaped profile is shown at FIGS. 2 and 3.
The connection is achieved by providing a plate 8 to close the end of the nozzle pipe 4 and by fixing (for example by forcing) the plate 8 into the C-shaped profile. This way possible vertical movement (as shown by arrow V) are prevented.
Then a U-shaped pin 9 is provided with one leg into holes of the C-shaped profile. The legs of the U-shaped pin are made to embrace the nozzle pipe 4. This way possible lateral movements (as shown by arrow L) are prevented.
During cleaning (this occurs periodically), compressed air is provided from the pressure vessel 7a (with the valve 7b open) through the pipe 6 into the nozzle pipe 4; this compressed air is ejected through the nozzles 5 as indicated by arrows A.
The compressed air has a higher pressure than the flue gas FG, such that without stopping the flue gas flow, the compressed air A can pass through the filter bags 3 and clean the filter bags 3.
Existing filters have some drawbacks.
In fact, possible horizontal movement of the nozzle pipe 4 as indicated by arrow H are not prevented. In some cases a stop can be provided, but it does not prevent horizontal vibrations in direction H that are generated for example when compressed air supply into the nozzle pipe 4 is started or interrupted. Vibrations in turn cause noise, wear and structural loads (fatigue).
In addition, the removal and insertion of the nozzle pipe 4 with the plate 8 connected to it into the C-shaped profile 2 is very troubling, such that assembling and disassembling of the nozzle pipe 4 is very time consuming. Assembling and disassembling of the nozzle pipe 4 is periodically needed for example for replacement of the filter bags 3.